1. Technical Field
The present invention relates to an image relay optical system used for a head mounted display mounted on the head and used and a virtual image display device including the image relay optical system.
2. Related Art
In recent years, as a virtual image display device for enabling formation and observation of a virtual image such as a head mounted display, various virtual image display devices of a type for guiding image light from a display device to the pupils of an observer with a light guide plate are proposed. As the light guide plate for such virtual image display device, there is a light guide plate including a light guide pipe that can cause plural optical modes having different light guide angles to proceed (see JP-T-2008-535001).
In an optical system disclosed in JP-T-2008-535001, a liquid crystal panel is illuminated with collimated light set to a different incident angle for each of the optical modes on condition that images in the plural optical modes are positionally shifted from one another. Display contents are changed in the optical modes and displays in the optical modes are sequentially executed to join images in the optical modes and obtain an overall image. In this case, an image in the center and images on the left and right included in the overall image have to be displayed while being changed with a time lag by one liquid crystal panel. As a result, a virtual image display device is complicated and an observation image is darkened.
There is also a virtual image display device for enabling observation of a virtual image with a light guide member in which a concave reflecting surface is provided accompanying a light incident surface and a convex reflecting surface is provided accompanying a light emitting surface. In the virtual image display device, it is unnecessary to join images with a time lag (see U.S. Pat. No. 7,477,453). An afocal system is formed by the two inclining reflecting surfaces. Aberration such as distortion is not reduced. Therefore, a projection optical system for collimate is complicated and image processing is necessary.